Inhalation toxicity studies were designed to study the toxicity and potential carcinogenicity of styrene and two congeners, alpha-methylstyrene and divinylbenzene. The research proposal has been prepared and reviewed and final protocols are being written. Studies on styrene will be initiated in September-October 1990. Studies will include evaluation of cell turnover in the respiratory tract and liver of rats and mice, the leukemia transplantation test in rats, and evaluation of micronuclei and immunotoxicity in mice. These studies are designed to provide scientific information on the comparative toxicity of styrene and its congeners and on possible mechanisms for potential carcinogenicity of these important chemicals.